Well, that sucks....
But in that case I would go ahead and space them 5'-10' apart with the disclaimer, "Most people I work for prefer them spaced close together so there's more of an instant screen, as opposed to waiting 5-10 years for them to fill in. So I'm guessing you'd like them spaced that close as well. I'll go ahead and do that. But understand that if you're still living here in about 7 years you're going to be paying me to remove every other tree at that time because they're going to be growing all into each other by that point."